Wireless sensor networks (WSN) are an emerging sensing system for communication. In a WSN, a plurality of sensor nodes are arranged in a discrete manner within a certain space for sensing other wireless devices, for example, a tag node or an identification node. Information can be transmitted between two sensors nodes, or from a sensor node to a tag node or an identification node, and vice versa.
A WSN can be used in a variety of applications, for example, in healthcare, home, military, or inventory management systems. A tag node in a WSN may save certain information associated with a target. For example, a tag node associated with a book may save basic information regarding the book including title, author, publisher, series number, et al. A tag node is usually placed in the neighborhood of its target or even attached to the target. Tag nodes may be moved with its target under certain circumstances. If a WSN system includes a large quantity of targets, the system would also use a large number of corresponding tag nodes. Therefore, tag nodes should be light weight, easy to use, and low cost. In view of these constraints, a tag node usually does not have an embedded power supply like a battery. Oftentimes, a tag node is equipped with an antenna to induce weak electric current and can only perform primitive operations.
Depending on the application, tag nodes may encompass sensitive and personal information. For example, in a medical WSN, a tag node may store personal data including name, social security number, blood type, symptoms, and chronological prescriptions of a person. This data should be well protected against unauthorized entities obtaining the data. Since the private data would be stored in the tag nodes and transmitted over an open WSN, the tag nodes that store the data should be able to reject unauthorized requests for retrieving the data, and the data should be kept in an encrypted manner during transmission.
Due to generally low power supplied to tag nodes, tag nodes may be computationally weak. Therefore conventional security mechanisms such as RSA asymmetric cryptosystem or AES encryption algorithm, both systems requiring tag nodes of high computation capability, are generally not applied to a WSN having weak tag nodes.
A conventional data retrieval scheme in a WSN is shown in FIG. 9. A sink node, which may be a server for a user to input certain information, sends out a query for certain data. The query may be encrypted in order to protect the query from exposure to attackers. A tag node may need to decrypt the query upon receipt. The tag node further decrypts stored data and performs searching over the data to find the correct response to the query. After finding the response, the tag node may encrypt the response in order to send it over the WSN. In addition, tag nodes with low-cost and simple design are vulnerable to physical attacks. The tag nodes should encrypt all of the data which was decrypted during the searching stage. Large computation power is involved during this data retrieval process. It is infeasible for a tag node having weak electrical current to perform such heavy computation.
To deal with these problems, the present invention proposes light-weight authentication and secret retrieval methods for communication systems.